The invention relates to a hydraulic power steering system for turning the steerable wheels of a vehicle.
Heavy-duty trucks use a hydraulic power steering system to provide power assist in turning the steerable wheels of the truck.
A conventional hydraulic power steering system includes a pump that flows high-pressure working fluid to a fluid motor. Power steering fluid is utilized as the working fluid. Power steering fluid is a specialized hydraulic oil supplied from a reservoir located within the engine compartment. The fluid is continuously recirculated through the system and may be replaced at regularly-scheduled maintenance intervals.
A major concern with hydraulic power steering systems is heat. The power steering reservoir is heated by its close proximity to the engine. If overheated power steering fluid is circulated through the steering system, pressure seals in the system may be damaged. Replacing damaged seals increases maintenance expenses and warranty costs.
As air pollution requirements for trucks become increasingly restrictive, engine temperatures are increasing. It is becoming more difficult to place the power steering reservoir in a location that provides adequate cooling. Furthermore, as the engine compartment becomes more crowded, finding a suitable location for the reservoir becomes even more difficult.
Therefore there is a need for an improved hydraulic power steering system that provides sufficient cooling of the working fluid utilized in the power steering system.